This invention relates to a control device for the shutter of a camera.
Various methods have been introduced for delaying shutter aperture closing timing by means of mechanical devices to thereby control the exposure time.
In the most commonly used method, a control member released during the shutter releasing operation successively releases an opening member and a closing member under the control of a mechanical delaying device. In this conventional method, although the shortest exposure time under the high speed setting and the relatively long exposure time under the low speed setting are accurately controlled, the control of the middle range of exposure times is unstable due to the scatter of the setting position of the mechanical delaying device. This is because under the high speed setting, the mechanical delaying device is at its rest position and the exposure time is controlled stably depending only on the speed of the control member whereas under the low speed setting, the error of the exposure time due to the scatter of the setting position of the mechanical delaying device is negligibly small relative to the exposure time; however, under the middle speed setting, the error of the exposure time due to the scatter of the setting position of the mechanical delaying device counts for much because the middle speed is controlled by the engagement of the mechanical delaying device for only a short period of time.
Disclosed in pending Application Ser. No. 787,204 now U.S. Pat. No. 4,134,659 issued Jan. 16. 1979, is an exposure time control device comprising a control system wherein the opening member releases the closing member during its opening motion in addition to the control system including a mechanical delaying device and being arranged so that the components are used selectively; however, the range of the exposure time controllable by controlling the timing of the release of the closing member by the opening member became limited as a consequence of the reduction of the stroke of the opening member due to the reduction of dimensions of shutters. Particularly, in controlling short exposure time, unstable motion of the opening member resulted in inaccurate exposure.